Half bridges may be used in power converters (e.g. in resonant power converters). Typical applications for such power converters are driver circuits for solid state lighting (SSL) devices such as Light Emitting Diode (LED) devices or Organic LED (OLED) devices. A half bridge typically comprises a high side switch coupled to an input voltage Vin and a low side switch coupled to ground, wherein the high side switch and the low side switch are switched in an alternating manner between an on-state and an off-state.
A commutation cycle of the half bridge typically comprises a high voltage phase during which the high side switch is in an on-state and during which the low side switch is in an off-state, and a low voltage phase during which the high side switch is in an off-state and during which the low side switch is in an on-state. The commutation cycles may be repeated at a pre-determined commutation cycle rate e.g. in the range of 20 kHz to 10 MHz. The high side and low side switches may be metal oxide semiconductor (MOS) transistors. e.g. PMOS and/or NMOS transistors.
The input voltage Vin of the half bridge may e.g. be derived from the mains power supply. By way of example, the input voltage Vin may be a rectified version of the mains power supply. As such, the input voltage may be a DC voltage at e.g. 400V. The midpoint of the half bridge (i.e. the coupling point between the high side switch and the low side switch) may be coupled via a coupling capacitor to a transformer for galvanic isolation of a subsequent device, e.g. a subsequent SSL device.
The present document describes a driver circuit for the high side switch of a half bridge. In particular, the present document describes a driver circuit for the high side switch of a half bridge, wherein the driver circuit is adapted to generate its supply voltage Vcc (e.g. 12V) directly from the input voltage Vin and at the same time to control the switching instants of the high side switch. As such, a cost effective driver circuit for the high side switch of a half bridge is described.